Eccentric mechanism for converting a rotary movement into a reciprocating rectilinear movement of variable amplitude

ABSTRACT

IN AN ECCENTRIC MECHANISM FOR CONVERTING THE INPUT ROTARY MOVEMENT OF A ROTARY MEMBER INTO AN OUTPUT RECIPROCATING LINEAR MOVEMENT, IN ORDER TO VARY ASYMMETRICALLY THE AMPLITUDE OF THE OUTPUT MOVEMENT, A SLOTTED CUP-LIKE ROTARY MEMBER DRIVES A CYLINDRICAL CRANK-PIN THROUGH AN ECCENTRIC LUG AND OFFSET SOCKET SO THAT ITS AXIS DESCRIBES AN ECCENTRICITY-SETTING CONE HAVING ITS CONTOUR DELIMITED BY A HIGH POSITION AND A LOW POSITION, AND HAVING A GENERATRIX PARALLEL TO THE AXIS OF ROTATION OF THE ROTARY MEMBER.

Oct. 26, 1971 c, s z ETAL 3,614,896

ECCENTRIC MECHANISM FOR CONVERTING A ROTARY MOVEMENT INTO A RECIPROCATING RECTILINEAR MOVEMENT OF VARIABLE AMPLITUDE Filed Aug. 11, 1969 2 Sheets-Sheet 2 3,614,896 ECCENTRIC MECHANISM FOR CONVERTING A ROTARY MOVEMENT INTO A RECIPROCATTNG RECTILINEAR MOVEMENT F VARIABLE AMPLITUDE Manuel Claude Sanz, Grand-Laney, Geneva, and Rene Weber, Geneva, Switzerland, assignors to Micromedic Systems, Inc., Philadelphia, Pa.

Filed Aug. 11, 1969, Ser. No. 849,025 Claims priority, application Switzerland, Aug. 16, 1968, 12,398/68 Int. Cl. F16h 21/18, 33/00 US. CI. 7442 6 Claims ABSTRACT OF THE DISCLOSURE In an eccentric mechanism for converting the input rotary movement of a rotary member into an output reciprocating linear movement, in order to vary asymmetrically the amplitude of the output movement, a slotted cup-like rotary member drives a cylindrical crank-pin through an eccentric lug and offset socket so that its axis describes an eccentricity-setting cone having its contour delimited by a high position and a low position, and having a generatrix parallel to the axis of rotation of the rotary member.

This invention relates to an eccentric mechanism for converting a rotary movement into a reciprocating rectilinear movement of variable amplitude, of the kind comprising an input shaft rigid with a rotary member, a crankpin driven by said rotary member in such a way as to describe a cone, a runner within which the crank-pin can slide, adjustment means permitting variation of the relative longitudinal position of the crank-pin relative to the runner, and an output member connected to the runner and constrained to move along a straight line perpendicular to the axis of the cone.

Numerous mechanisms of this kind are known and they permit a symmetrical variation to be obtained of the amplitude of the reciprocating movement of the output member, i.e., the travel of the output member always takes place on opposite sides of an invariable means position: the high and low dead points are always, for a given setting of the amplitude, symmetrical with respect to this means position. Now in certain cases it is useful for the high dead points (or the low dead points) always to coincide, whatever may be the amplitude, with an invariable position; the travel of the output member must then take place on opposite sides of a mean position which varies as a function of the amplitude.

An object of the present invention is to porvide an cecentric mechanism in which the amplitude of movement of the output member may be varied in as asymmetrical manner. For this purpose, according to the invention there is provided a mechanism of the kind defined wherein the crank-pin is a cylindrical rod one end of which is secured to a cross-piece mounted on a transverse pivot whose ends slide in two longitudinal slideways provided within the said rotary member and contained in a meridian plane of the latter, and the other end of whichcarries a ball cooperating with a socket offset relative to the axis of rotation of the rotary member and carried by a slide member capable of sliding axially in a slideway which is parallel to this axis of rotation and which prevents it from rotating around the latter, the said cross-piece and socket being arranged so that the cone which is described by the axis of the crank-pin under the effect of the rotation of the rotary member has a generatrix which is parallel to the said axis of rotation, wherein the said runner comprises a member which is provided with an aperture delimited by two opposed conical surfaces having apical openings equal nited States fatent to those of said cone and which is guided by a double guideway comprising a first movable slideway which permits said member to slide in a direction perpendicular to the plane containing said axis of rotation and said parallel generatrix, and which is carried by a pair of blocks slideable in a second fixed slideway and which permits the first to slide along the said straight line at right angles to the axis of said cone, said output member being rigid with said pair of blocks. Conveniently the said adjustment means comprise a first screw threaded member coaxial with said axis of rotation and cooperating with a second screw threaded member mounted on a fixed bearing.

One form of embodiment of the invention given by way of example only, is described below with reference to the accompanying drawings in which:

FIG. 1 is a longitudinal section;

FIG. 2 is a diagram showing two positions of one element;

FIG. 4, 5 and 6 are cross sections along the lines IVIV, V-V, VI-VI respectively of FIG. 1.

The mechanism shown in FIG. 1 is housed in a cylindrical casing 1 which is itself carried by a framework 2. This mechanism comprises an input shaft 3 which by means not shown is rotatably driven as indicated by the arrow 4. This input shaft is rigid with a rotary member 5 rotating on bearings 6, 7. The rotary member 5 which is hollowed out in the form of a cup, is provided with slots 8, 9 in which can slide blocks 10, 11 carried by the ends of a transverse pivot 12. The slots 8, 9 are arranged in a meridian plane of ther otary member 5, so that the trans verse pivot 12 is directed along a diameter of this rotary member. The transverse pivot is thus driven by the rotation of the member 5 around the axis 13 of the latter, and it can slide axially within the latter. A crank-pin 14, constituted by a cylindrical rod, carries at one of its ends a cross-piece 15 in the form of a half-moon, which is secured thereto by a pin 16 and which is traversed by the transverse pivot 12 around which it can pivot. The other end of the crank-pin 14 carires an eccentric lug 17 on which is secured a ball 18 of a ball and socket joint. This ball is held in a socket 19 provided in a slide member 20 and it is retained in this socket by a plate 21 secured to the slide member by screws 22. The socket 19 thus houses the ball of the crank-pin 14 and this socket is offset relative to the axis 13. The distance between the axis 25 of the crank-pin 14 and the transverse pivot 12, on the one hand, and the eccentricity setting of the socket 19 in the slide member 22 on the other hand, are so chosen that taking into account the ecentric-setting of the lug 17, there exists an angular position of the rotary member 5 called the high position in which the axis of the crank-pin is parallel to the axis of rotation 13. Moreover, the angular connection of the crank-pin 14 to its cross-piece 15 is such that when it is in this high position, the lug 17 and the axis 25 are located in the same meridian plane as the rotary member 5, a meridian plane which, in FIG. 1 coincides with the plane of the drawing.

It will be seen that in the course of rotation of the member 5, the crank-pin 14 passes through a low position 14 shown in bro-ken lines (see FIG. 2) and that, upon a complete revolution, its axis 25 describes a so-called eccentricity-setting cone, the apparent conour of which is delimited by the high position 25 and the low position 25' of this axis and which has a generatrix 25 parallel to the axis of rotation 13. This eccentricity-setting cone has an apical opening A and its axis 26 is inclined relative to the axis of rotation 13; it meets the latter at the location where the transverse pivot 12 intersects it.

The slide member 20 is arranged in such a way as to be axially displaceable in the housing 1 which acts as a slideway therefor and a radial stud 23 which extends through a longitudinal slot 24 provided in the housing and prevents it from turning around the axis 13; the centre of the socket is thus displaced along a straight line parallel to the axis of rotation 13.

On the crank-pin 14 is mounted a runner constituted by a member 27 provided with a hole delimited by two opposed conical surfaces 28, 29 (FIG. 3) each of which has an apical opening equal to the apical opening A of the eccentricity setting 25, 25'. This arrangement permits the crank-pin to rotate and to slide in this runner while causing it to move without play over its conical movement. The member 27 is held between two rods 30, 31 which constitute a first slideway enabling it to slide in a direction 32 perpendicular to the meridian plane defined by the axis of rotation 13- and by the high generatrix 25 of the eccentricity-setting cone. These two rods extend through the housing 1 via two slots 33, 34 and are assembled by means of two crosspieces 35, 36 (FIG. These cross-pieces constitute blocks which in their turn slide in two grooves 37, 38 constituting a second slideway which enables the first to move in a direction 39 perpendicular to the ads 26 of the cone eccentricity. The rod 31 extends beyond the blocks 35, 36 and its ends 40, 41 serve as pivots on which is pivoted a yoke 42. In the example described, this yoke is in turn pivoted on a lever 43 guided in a sliding hearing 44 arranged in the framework 2.

The slide member 20 is rigid with a rod 45 which constitutes the end of a screw 46 and which cooperates with nut 47 carried by a sleeve 48. This latter rotates in a bearing constituted by three resilient rods 51, 52, 53 (FIG. 6) located in a plane perpendicular to the axis of rotation 13 and arranged in such a way as to form a triangular frame which circumscribes this sleeve: the ends 5459 of these rods are held in a bearing support 60 while their middle points 61, 62, 63 cooperate with a circular groove 64 in the sleeve 48. This triangular frame thus constitutes a resilient hearing, which may be advantageous when there is a risk of alignment defects and when it is desirable to eliminate the stresses which may result therefrom.

The sleeve 48 carries a knob 65 secured to it by a pin 66. The rod 45, screw 46, nut 47, sleeve 48 and knob 65 constitute control means enabling the axial position of slide member 20, and consequently of crankpin 14 and cross-piece 15 to be varied.

The operation of this mechanism will be readily understood. As has already been described, the crank-pin 14, due to the fact that it is angularly rigid with the rotary member 5 via the slots 8, 9, transverse pivot 12 and cross-piece 15, rotates around the socket 19, so that its axis 25 describes the eccentricity-setting cone shown diagrammatically by the lines 25, 25' which represent two particular generatrices, the high generatrix 25 and the low generatrix 25'. Consequently the centre of the runner 27, which is guided in the slideways 30, 31 and 37, 38 cannot leave a plane perpendicular to the axis 26 of this cone, and is obliged to describe the circle constituted by the intersection of the cone with the plane. The output member has thus imparted thereto in the direction 39 a rectilinear reciprocating movement having an amplitude which is equal to the radius of this circle, the total travel being equal to the diameter. If, by manipulating the nut 47 by means of knob 65, the axial position of slide member 20, and thus of crank-pin 14 and cross-piece 15 is varied, the distance between the apex of the cone of eccentricity 25, 25' and the plane in which the runner moves is also varied, this plane being defined by the directions 32 and 39. In this way the diameter of the circle constituted by the intersection of this cone and plane is varied and hence the amplitude of the alternating movement communicated to the output member is also varied. As the dimensions of the various parts have been chosen in such a way that the high generatrix 25 of the eccentricitysetting cone may lie parallel to the axis of rotation 13, the high dead point of this reciprocating movement is independent of the axial position of the crank-pin: there is thus obtained an asymmetric variation of the amplitude and the mean position, on either side of which the movement of the output member takes place, varies in the same manner as the amplitude.

The modification in amplitude may be made both while the rotary member is rotating as well as when it is stationary. It may be advantageous, in the latter case, to permanently immobilize the crank-pin in its high position, where its axis 25 coincides with the high generatrix of the cone of eccentricity. The modification of the axial position of the slide member 20 necessary for changing the amplitude then has no effect on the output member which remains perfectly stationary. In order to arrive with certainty at this result, the mechanism is provided with a resilient detent which may be constituted by a ball trapped in a socket 71 arranged in the casing 1. This ball is urged by a spring 72 so as to cooperate with a longitudinal slot 73 on the external lateral surface of the rotary member 5 in a suitable angular position. This arrangement is advantageous when the mechanism is used to actuate a piston pump which transports a fluid; one can thus be certain, by modifying the amplitude adjustment when the mechanism is stationary, that this modification of adjustment will not cause unwanted displacements of fluid. It is thus an advantage which renders this mechanism particularly suitable for actuating pumps for dosing microanalysis apparatus, in particular bio-chemical microanalysis.

The mounting of the ball 18 on the lug 17 offset relative to the axis 25 of the crank-pin is not indispensable. This arrangement is provided in order to permit the runner to slide up to the moment when the plane in which it moves passes through the centre 50 of the eccentricity-setting cone, i.e. to permit the amplitude adjustment range to be extended up to the value zero. If this requirement is not necessary, the ball can then be fixed in a position coaxial with the axis 25, i.e. to use a central lug 17.

It is, of course, possible to provide a system enabling the axial position of the slide member 20 to be measured and this system can be graduated directly according to the value of the amplitude.

Finally, it may be advantageous to limit the axial movement of the slide member 20 in order to prevent the runner from coming into contact with the ball 18 of with the cross-piece 15: this may be achieved for example by suitably dimensioning the length of the slot 24 and positioning it longitudinally in the desired manner.

We claim:

1. An eccentric mechanism for the conversion of a rotary movement into a reciprocating rectilinear movement of variable amplitude comprising an input shaft rigid with a rotary member, a crank-pin driven by said rotary member so as to describe a cone, a runner within which said crank-pin can slide, adjustment means permitting variation of the relative longitudinal position of said crank-pin relative to said runner and an output member connected to said runner and constrained to move along a straight line perpendicular to the axis of said cone, said crank-pin being constituted by a cylindrical rod, one end of which is secured to a cross-piece mounted on a transverse pivot whose ends slide in two longitudinal slideways provided within said rotary member and contained in a meridian plane of the latter, and the other end of which carries a ball cooperating with a socket offset relative to the axis of rotation of the rotary member and carried by a slide member capable of sliding axially in a slideway which is parallel to said axis of rotation and which prevents it from rotating around the latter, the said cross-piece and socket being arranged so that the said cone has a generatrix parallel to said axis of rotation, the said runner comprising a member having walls defining an aperture, said walls comprising two opposed conical surfaces having boundary means defining apical openings equal to those of said cone, and which is guided by a double guideway comprising a first movable slideway which permits said member to slide in a direction perpendicular to the plane containing said axis of rotation and said parallel generatrix, and which is carried by a pair of blocks sliding in a second fixed slideway which permits the first to slide along the said straight line at right angles to the axis of said cone, said output member being rigid with said pair of blocks.

2. Mechanism according to claim 1 wherein the adjustment means comprise a first screw threaded member c0- axial with said axis of rotation and cooperating with a second screw threaded member mounted on a fixed bearing.

3. Mechanism according to claim 2 comprising a resilient detent adapted to locate accurately the angular position of the said rotary member which corresponds to the passage of the said crank-pin in the position where its axis coincides with the said parallel generatrix.

4. Mechanism according to claim 2 wherein the said fixed bearing is resilient.

5. Mechanism according to claim 2 wherein the said fixed bearing comprises at least three resilient rods arranged in a plane perpendicular to the said axis of rotation in such a way as to form a triangular frame circumscribing a bush carrying the said second screw threaded member, the ends of these rods being fixed and their mid-points cooperating with a circular groove arranged in said sleeve.

6. Mechanism according to claim 2 wherein relative to the axis of the said crank-pin, the said ball is offset in a direction perpendicular to the said transverse pivot and in a direction opposite to the latter.

References Cited UNITED STATES PATENTS 1,679,884 8/1928 Thomas 74-60 1,901,981 3/1933 Ousback 74--60 2,824,455 2/1958 Ristow et al. 7460 3,359,810 12/1967 Hansen 7460 WILLIAM F. ODEA, Primary Examiner W. S. RATLIFF, 1a., Assistant Examiner US. Cl. X.R. 

